This document provides details about the internal and external structures of insect wings. It discusses the various veins and folds that make up the wing, including the costa, radius, media, cubitus, anal veins, and cross veins. It describes how the wings are composed of a membrane supported by a system of veins, and how the veins contain nerves, trachea, and hemolymph. It also summarizes the different regions of the wing, including the remigium, vannus, jugum, and axillary area.

1. Founded 1991 by Md. Alimullah Miyan
Report on
Insect’s wing
This report is prepared for partial fulfillment of
Entomology
Prepared for
Prof. Dr. Emdadul Haque
Department of Agriculture Sciences
Prepared by
Md.Amman Ali
ID:15309038
Program: BSAg
Semester: Summer-2016
Md.Aminul Haque
ID: 15309039
Program: BSAg
Semester: Summer-2016

2. Introduction
Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on
the second and third thoracicsegments (the mesothorax and metathorax), and the two pairs are often
referred to as the forewings and hindwings, respectively, though a few insects lack hindwings, even
rudiments. The wings are strengthened by a number of longitudinal veins,
which often have cross-connections that form closed "cells" in the
membrane (extreme examples include Odonata and Neuroptera). The
patterns resulting from the fusion and cross-connection of the wing veins
are often diagnostic for different evolutionary lineages and can be used
for identification to the family or even genus level in many orders of
insects.
The physical dynamics of flight are composed of direct and indirect flight.
Those species that employ direct flight have wing muscles directly
attached to the wing base, so that a small downward movement of the
wing base lifts the wing itself upward. However,insects with indirect
flight have muscles that attach to the thorax and deform it; since the wings
are extensions of the thoracic exoskeleton, the deformations of the thorax
cause the wings to move as well.
The wings may be present in only one sex (often the male) in some groups
such as velvet ants and Strepsiptera, or selectively lost in "workers"
of social insects such as ants and termites. Rarely, the female is winged
but the male not, as in fig wasps. In some cases,wings are produced only
at particular times in the life cycle, such as in the dispersal phase
of aphids. Beyond the mere presence/absence of wings, the structure and
colouration will often vary with morphs, such as in the aphids, migratory
phases of locusts and in polymorphicbutterflies.
At rest, the wings may be held flat, or folded a number of times along specific patterns; most typically, it
is the hindwings which are folded, but in a very few groups such as vespid wasps,it is the forewings.
How and why insect wings evolved is not well understood. Three main theories on the origins of insect
flight are that wings developed from paranotal lobes, extensions of the thoracic terga; that they are
modifications of movable abdominal gills as found on aquatic naiads of mayflies; and that insect wings
arose from the fusion of pre-existing endite and exite structures each with pre-existing articulation and
tracheation.
Internal
Each of the wings consists of a thin membrane supported by a system of veins. The membrane is formed
by two layers of integument closely apposed, while the veins are formed where the two layers remain
separate and the lower cuticle may be thicker and more heavily sclerotized.
Within each of the major veins there is a nerve and a trachea,and, since the
cavities of the veins are connected with the hemocoel, hemolymph can flow
into the wings. Also veins are the wing's lumen, being an extension of the
hemocoel, which contains the tracheae,nerves,and hemolymph. As the wing
develops, the dorsal and ventral integumental layers become closely apposed
over most of their area forming the wing membrane. The remaining areas form channels, the future veins,
in which the nerves and tracheae may occur. The cuticle surrounding the veins becomes thickened and
more heavily sclerotized to provide strength and rigidity to the wing. Two types of hair may occur on the
wings: microtrichia, which are small and irregularly scattered,and macrotrichia, which are larger,

3. socketed, and may be restricted to veins. The scales of Lepidoptera and Trichoptera are highly modified
macrotrichia.
Venation
In some very small insects, the venation may be
greatly reduced. In Chalcidoidea (Chalcid
wasps),for instance, only the subcosta and part
of the radius are present. Conversely, an increase
in venation may occur by the branching of
existing veins to produce accessory veins or by
the development of additional, intercalary veins
between the original ones, as in the wings
of Orthoptera (grasshoppers and crickets). Large numbers of cross-veins are present in some insects, and
they may form a reticulum as in the wings of Odonata(dragonflies and damselflies) and at the base of the
forewings of Tettigonioidea and Acridoidea (katydids and grasshoppers respectively)
The archedictyon is the name given to a hypothetical scheme of wing venation proposed for the very first
winged insect. It is based on a combination of speculation and fossil data. Since all winged insects are
believed to have evolved from a common ancestor, the archediction represents the "template" that has
been modified (and streamlined) by natural selection for 200 million years. According to current dogma,
the archedictyon contained 6–8 longitudinal veins. These veins (and their branches) are named according
to a system devised by John Comstock and George Needham—the Comstock-Needham System:
 Costa (C) – the leading edge of the wing
 Subcosta (Sc) – second longitudinal vein (behind the costa),typically unbranched
 Radius (R) – third longitudinal vein, one to five branches reach the wing margin
 Media (M) – fourth longitudinal vein, one to four branches reach the wing margin
 Cubitus (Cu) – fifth longitudinal vein, one to three branches reach the wing margin
 Anal veins (A1, A2, A3) – unbranched veins behind the cubitus
The costa (C) is the leading marginal vein on most insects, although sometimes there is a small vein
above the costa called the precosta, although in almost all extant insects, the precosta is fused with the
costa; The costa rarely ever branches because is at the leading edge, which is associated at its base with
the humeral plate. The trachea of the costal vein is perhaps a branch of the subcostal trachea. Located
after the costa is the third vein, the subcosta,which branches into two separate veins: the anterior and
posterior. The base of the subcosta is associated with the distal end of the neck of the first axillary (see
section below). The fourth vein is the radius (R), which is branched into five separate veins. The radius is
generally the strongest vein of the wing. Toward the middle of the wing, it forks into a first undivided
branch (R1) and a second branch, called the radial sector (Ra),which subdivides dichotomously into four
distal branches (R2, R3, R4, R5). Basally, the radius is flexibly united with the anterior end of the second
axillary (2Ax).
The fifth vein of the wing is the media. In the archetype pattern (A),the media forks into two main
branches: a media anterior (MA), which divides into two distal branches (MA1, MA2), and a median
sector,or media posterior (MP),which has four terminal branches (M1, M2, M3, M4). In most modern
insects the media anterior has been lost, and the usual "media" is the four-branched media posterior with
the common basalstem. In the Ephemerida, according to present interpretations of the wing venation,
both branches of the media are retained, while in Odonata the persisting media is the primitive anterior
branch. The stem of the media is often united with the radius, but when it occurs as a distinct vein its base
is associated with the distal median plate (m') or is continuously sclerotized with the latter. The cubitus,
the sixth vein of the wing, is primarily two branched. The primary forking of the takes place near the base
of the wing, forming the two principal branches (Cu1, Cu2). The anterior branch may break up into a
number of secondary branches,but commonly it forks into two distal branches. The second branch of the

4. cubitus (Cu2) in Hymenoptera, Trichoptera, and Lepidoptera was mistaken by Comstock and Needham
for the first anal. Proximally the main stem of the cubitus is associated with the distal median plate (m') of
the wing base.Postcubitus (Pcu) is the first anal of the Comstock and Needham system. The Postcubitus,
however, has the status of an independent wing vein and should be recognized as such. In nymphal wings,
its trachea arises between the cubital trachea and the group of vannal tracheae. In the mature wings of
more generalized insect the Postcubitus is always associated proximally with the cubitus and is never
intimately connected with the flexor sclerite (3Ax) of the wing base. In Neuroptera,Mecoptera,and
Trichoptera the postcubitus may be more closely associated with the vannal veins, but its base is always
free from the latter. The postcubitus is usually unbranched; it is primitively two branched. The vannal
veins (lV to nV) are the anal veins that are immediately associated with the third axillary, and which are
directly affected by the movement of this sclerite that brings about the flexion of the wings. In number the
vannal veins vary. from 1 to 12, according to the expansion of the vannal area of the wing. The vannal
tracheae usually arise from a common trachealstem in nymphal insects, and the veins are regarded as
branches of a single anal vein. Distally the vannal veins are either simple or branched. Jugal Veins (J) of
the jugal lobe of the wing is often occupied by a network of irregular veins, or it may be entirely
membranous; but sometimes it contains one or two distinct small veins, the first jugal vein, or vena
arcuata,and the second jugal vein, or vena cardinalis (2J).
 C-Sc cross-veins – run between the costa and subcosta
 R cross-veins – run between adjacent branches of the radius
 R-M cross-veins – run between the radius and media
 M-Cu cross-veins – run between the media and cubitus
All the veins of the wing are subject to secondary forking and to union by cross-veins. In some orders of
insects the cross-veins are so numerous that the whole venational pattern becomes a close network of
branching veins and cross-veins. Ordinarily, however, there is a definite number of cross-veins having
specific locations. The more constant cross-veins are the humeral cross-vein (h) between costa and
subcosta, the radial cross-vein (r) between R and the first fork of Rs,the sectorial cross-vein (s) between
the two forks of R8, the median cross-vein (m–m) between M2 and M3, and the mediocubital cross-vein
(m-cu) between media and cubitus.
The veins of insect wings are characterized by a convex-concave placement, such as those seen in
mayflies (i.e., concave is "down" and convex is "up") which alternate regularly and by its triadic type of
branching; whenever a vein forks there is always an interpolated vein of the opposite position between the
two branches. A concave vein will fork into two concave veins (with the interpolated vein being convex)
and the regular alteration of the veins is preserved.[6]
The veins of the wing appear to fall into an
undulating pattern according to whether they have a tendency to fold up or down when the wing is
relaxed. The basal shafts of the veins are convex, but each vein forks distally into an anterior convex
branch and a posterior concave branch. Thus the costa and subcosta are regarded as convex and concave
branches of a primary first vein, Rs is the concave branch of the radius, posterior media the concave
branch of the media, Cu1 and Cu2 are respectively convex and concave, while the primitive Postcubitus
and the first vannal have each an anterior convex branch and a posterior concave branch. The convex or
concave nature of the veins has been used as evidence in determining the identities of the persisting distal
branches of the veins of modern insects, but it has not been demonstrated to be consistent for all wings.
Field
Wing areas are delimited and subdivided by fold-lines along which the
wing can fold, and flexion-lines along which the wing can flex
during flight. The fundamental distinction between the flexion-lines
and the fold-lines is often blurred, as fold-lines may permit some
flexibility or vice versa. Two constants that are found in nearly all
insect wings are the claval (a flexion-line) and jugal folds (or fold line);

5. forming variable and unsatisfactory boundaries. Wing foldings can very complicated, with transverse
folding occurs in the hind wings ofDermaptera and Coleoptera, and in some insects the anal area can be
folded like a fan.[4]
There are about four different fields found on the insect wings:
Remigium
Anal area (vannus)
Jugal area
Axillary area
Alula
Most veins and crossveins occur in the anterior area of the remigium, which is responsible for most of the
flight, powered by the thoracic muscles. The posterior portion of the remigium is sometimes called
the clavus; the two other posterior fields are the anal and jugal ares. When the vannal fold has the usual
position anterior to the group of anal veins, the remigium contains the costal, subcostal, radial, medial,
cubital, and postcubital veins. In the flexed wing the remigiumturns posteriorly on the flexible basal
connection of the radius with the second axillary, and the base of the mediocubital field is folded medially
on the axillary region along the plica basalis (bf) between the median plates (m, m') of the wing base.
The vannus is bordered by the vannal fold, which typically occurs between the postcubitus and the first
vannal vein. In Orthoptera it usually has this position. In the forewing of Blattidae, however, the only fold
in this part of the wing lies immediately before the postcubitus. In Plecoptera the vannal fold is posterior
to the postcubitus, but proximally it crosses the base of the first vannal vein. In the cicada the vannal fold
lies immediately behind the first vannal vein (lV). These small variations in the actual position of the
vannal fold, however, do not affect the unity of action of the vannal veins, controlled by the flexor sclerite
(3Ax), in the flexion of the wing. In the hind wings of most Orthoptera a secondary vena dividens forms a
rib in the vannal fold. The vannus is usually triangular in shape, and its veins typically spread out from
the third axillary like the ribs of a fan. Some of the vannal veins may be branched, and secondary veins
may alternate with the primary veins. The vannal region is usually best developed in the hind wing, in
which it may be enlarged to form a sustaining surface,as in Plecoptera and Orthoptera. The great fanlike
expansions of the hind wings of Acrididae are clearly the vannal regions, since their veins are all
supported on the third axillary sclerites on the wing bases,though Martynov (1925) ascribes most of the
fan areas in Acrididae to the jugal regions of the wings. The true jugum of the acridid wing is represented
only by the small membrane (Ju) mesad of the last vannal vein. The jugum is more highly developed in
some other Orthoptera, as in the Mantidae. In most of the higher insects with narrow wings the vannus
becomes reduced, and the vannal fold is lost, but even in such cases the flexed wing may bend along a
line between the postcubitus and the first vannal vein.
The Jugal Region, or Neala,is a region of the wing that is usually a small membranous area proximal to
the base of the vannus strengthened by a few small, irregular veinlike thickenings; but when well
developed it is a distinct section of the wing and may contain one or two jugal veins. When the jugal area
of the forewing is developed as a free lobe, it projects beneath the humeral angle of the hind wing and
thus serves to yoke the two wings together. In the Jugatae group of Lepidoptera it bears a long finger-like
lobe. The jugal region was termed the neala ("new wing") because it is evidently a secondary and recently
developed part of the wing.
The axillary region is region containing the axillary sclerites has in general the form of a scalene triangle.
The base of the triangle (a-b) is the hinge of the wing with the body; the apex (c) is the distal end of the
third axillary sclerite; the longer side is anterior to the apex. The point d on the anterior side of the
triangle marks the articulation of the radial vein with the second axillary sclerite. The line between d and
c is the plica basalis (bf), or fold of the wing at the base of the mediocubital field.
 At the posterior angle of the wing base in some Diptera there is a pair of membranous lobes
(squamae, or calypteres) known as the alula. The alula is well developed in the house fly. The outer

6. squama (c) arises from the wing base behind the third axillary sclerite (3Ax) and evidently represents
the jugal lobe of other insects (A, D); the larger inner squama (d) arises from the posterior scutellar
margin of the tergum of the wing-bearing segment and forms a protective, hoodlike canopy over the
halter. In the flexed wing the outer squama of the alula is turned upside down above the inner
squama, the latter not being affected by the movement of the wing. In many Diptera a deep incision
of the anal area of the wing membrane behind the single vannal vein sets off a proximal alar lobe
distal to the outer squama of the alula.
Joints
The various movements of the wings, especially in insects that flex the wings horizontally over the back
when at rest, demand a more complicated articular
structure at the wing base than a mere hinge of the wing
with the body. Each wing is attached to the body by a
membranous basal area,but the articular membrane
contains a number of small articular sclerites, collectively
known as the pteralia. The pteralia include an anterior
humeral plate at the base of the costal vein, a group of
axillaries (Ax) associated with the subcostal, radial, and vannal
veins, and two less definite median plates (m, m') at the base
of the mediocubital area. The axillaries are specifically developed only in the wing-flexing insects, where
they constitute the flexor mechanism of the wing operated by the flexor muscle arising on the pleuron.
Characteristic of the wing base is also a small lobe on the anterior margin of the articular area proximal to
the humeral plate, which, in the forewing of some insects, is developed into a large, flat, scale-like flap,
the tegula, overlapping the base of the wing. Posteriorly the articular membrane often forms an ample
lobe between the wing and the body, and its margin is generally thickened and corrugated, giving the
appearance of a ligament, the so-called axillary cord, continuous mesally with the posterior marginal
scutellar fold of the tergal plate bearing the wing.
The articular sclerites, or pteralia, of the wing base of the wing-flexing insects and their relations to the
body and the wing veins, shown diagrammatically, are as follows:
Humeral plates
First Axillary
Second Axillary
Third Axillary
Fourth Axillary
Median plates (m, m')
The humeral plate is usually a small sclerite on the anterior margin of the wing base,movable and
articulated with the base of the costal vein. Odonata have their humeral plate greatly enlarged, with two
muscles arising from the episternum inserted into the Humeral plates and two from the edge of the
epimeron inserted into the axillary plate.
The first axillary sclerite (lAx) is the anterior hinge plate of the wing base. Its anterior part is supported on
the anterior notal wing process of the tergum (ANP); its posterior part articulates with the tergal margin.
The anterior end of the sclerite is generally produced as a slender arm, the apex of which (e) is always
associated with the base of the subcostal vein (Sc), though it is not united with the latter. The body of the
sclerite articulates laterally with the second axillary. The second axillary sclerite (2Ax) is more variable in
form than the first axillary, but its mechanical relations are no less definite. It is obliquely hinged to the
outer margin of the body of the first axillary, and the radial vein (R) is always flexibly attached to its
anterior end (d). The second axillary presents both a dorsal and a ventral sclerotization in the wing base;
its ventral surface rests upon the fulcral wing process of the pleuron. The second axillary, therefore, is the
pivotal sclerite of the wing base,and it specifically manipulates the radial vein.

7. The third axillary sclerite (3Ax) lies in the posterior part of the articular region of the wing. Its form is
highly variable and often irregular, but the third axillary is the sclerite on which is inserted the flexor
muscle of the wing (D). Mesally it articulates anteriorly (f) with the posterior end of the second axillary,
and posteriorly (b) with the posterior wing process of the tergum (PNP),or with a small fourth axillary
when the latter is present. Distally the third axillary is prolonged in a process which is always associated
with the bases of the group of veins in the anal region of the wing here termed the vannal veins (V). The
third axillary, therefore,is usually the posterior hinge plate of the wing base and is the active sclerite of
the flexor mechanism, which directly manipulates the vannal veins. The contraction of the flexor muscle
(D) revolves the third axillary on its mesal articulations (b, f) and thereby lifts its distal arm; this
movement produces the flexion of the wing. The Fourth Axillary sclerite is not a constant element of the
wing base. When present it is usually a small plate intervening between the third axillary and the posterior
notal wing process and is probably a detached piece of the latter.
The median plates (m, m') are also sclerites that are not so definitely differentiated as specific plates as are
the three principal axillaries, but nevertheless they are important elements of the flexor apparatus. They
lie in the median area of the wing base distal to the second and third axillaries and are separated from
each other by an oblique line (bf) which forms a prominent convex fold during flexion of the wing. The
proximal plate (m) is usually attached to the distal arm of the third axillary and perhaps should be
regarded as a part of the latter. The distal plate (m') is less constantly present as a distinct sclerite and may
be represented by a general sclerotization of the base of the mediocubital field of the wing. When the
veins of this region are distinct at their bases,they are associated with the outer median plate.
Muscles
The muscles that control flight in insects can take up to 10% to 30% of the total body mass. The muscles
that control flight vary with the two types of flight found in insects: indirect and direct. Insects that use
first, indirect, have the muscles attach to the tergum instead of the wings, as the name suggests. As the
muscles contract, the thoracic box becomes distorted, transferring the energy to the wing. There are two
"bundles" of muscles, those that span parallel to the tergum, the dorsolongitudinals, and those that are
attached to the tegum and extend to the sternum, the dorsoventrals.[7]
In direct muscle, the connection is
directly from the pleuron (thoracic wall) to individual sclerites located at the base of the wing. The
subalar and basalar muscles have ligament attachments to the subalar and basalar sclerites. Here resilin, a
highly elastic material, forms the ligaments connecting flight muscles to the wing apparatus.
In more derived orders of insects, such as Diptera (flies) and Hymenoptera (wasp),the indirect muscles
occupy the greatest volume of the pterothorax and function as the primary source of power for the
wingstroke. Contraction of the dorsolongitudinal muscles causes the severe arching of the notum which
depresses the wing while contraction of the dorsoventral muscles causes opposite motion of notum. Other
more primitive insects, such as Orthoptera (locusts), Coleoptera (beetles), and Odonata (dragonflies) use
direct muscles that are responsible for developing the needed power for the up and down strokes.
Insect wing muscle is a strictly aerobic tissue. Per unit protein it consumes fuel and oxygen at rates taking
place in a very concentrated and highly organized tissue so that the steady-state rates per unit volume
represent an absolute record in biology. The fuel and oxygen rich blood is carried to the muscles through
diffusion occurring in large amounts, in order to maintain the high level of energy used during flight.
Many wing muscles are large and may be as large as 10 mm in length and 2 mm in width. Moreover, in
some Diptera the fibres are of giant dimensions. For instance, in the very active Rutilia, the cross-section
is 1800 µm long and more than 500 µm wide. The transport of fuel and oxygen from the surroundings to
the sites of consumption and the reverse transport of carbon dioxide therefore represent a challenge to the
biologist both in relation to transport in the liquid phase and in the intricate system of air tubes, i.e. in the
trachealsystem.
Coupling, folding, and other features

8. In many insect species, the fore and hind wing are coupled together, which improves the aerodynamic
efficiency of flight. The most common coupling mechanism (e.g.,Hymenoptera and Trichoptera) is a row
of small hooks on the forward margin of the hind wing, or "hamuli", which lock onto the fore wing,
keeping them held together (hamulate coupling). In some other insect species
(e.g., Mecoptera,Lepidoptera, and some Trichoptera) the jugal lobe of the fore wing covers a portion of
the hind wing (jugal coupling), or the margins of the fore and hind wing overlap broadly (amplexiform
coupling), or the hindwing bristles, or frenulum, hook under the retaining structure or retinaculum on the
forewing.
When at rest,the wings are held over the back in most insects, which may involve longitudinal folding of
the wing membrane and sometimes also transverse folding. Folding may sometimes occur along the
flexion lines. Though fold lines may be transverse,as in the hind wings of beetles and earwigs, they are
normally radial to the base of the wing, allowing adjacent sections of a wing to be folded over or under
each other. The commonest fold line is the jugal fold, situated just behind the third anal vein, although,
most Neoptera have a jugal fold just behind vein 3A on the forewings. It is sometimes also present on the
hindwings. Where the anal area of the hindwing is large, as in Orthoptera and Blattodea, the whole of this
part may be folded under the anterior part of the wing along a vannal fold a little posterior to the claval
furrow. In addition, in Orthoptera and Blattodea, the anal area is folded like a fan along the veins, the anal
veins being convex, at the crests of the folds, and the accessory veins concave. Whereas the clavalfurrow
and jugal fold are probably homologous in different species, the vannal fold varies in position in different
taxa. Folding is produced by a muscle arising on the pleuron and inserted into the third axillary sclerite in
such a way that, when it contracts, the sclerite pivots about its points of articulation with the posterior
notal process and the second axillary sclerite.
As a result, the distal arm of the third axillary sclerite rotates upwards and inwards, so that finally its
position is completely reversed. The anal veins are articulated with this sclerite in such a way that when it
moves they are carried with it and become flexed over the back of the insect. Activity of the same muscle
in flight affects the power output of the wing and so it is also important in flight control. In orthopteroid
insects, the elasticity of the cuticle causes the vannal area of the wing to fold along the veins.
Consequently, energy is expended in unfolding this region when the wings are moved to the flight
position. In general, wing extension probably results from the contraction of muscles attached to the
basalar sclerite or, in some insects, to the subalar sclerite.
Flight
Two groups of relatively large insects, the Ephemeroptera (mayflies) and the Odonata (dragonflies and
damselflies) have the flight muscles attached directly to their wings; the wings can beat no faster than the
rate at which nerves can send impulses to command the muscles to beat.[10]
All other living winged
insects fly using a different mechanism, involving indirect flight muscles which cause the thorax to
vibrate; the wings can beat faster than the rate at which the
muscles receive nerve impulses. This mechanism evolved once,
and is the defining feature (synapomorphy) for the
infraclass Neoptera.
There are two basic aerodynamic models of insect flight. Most
insects use a method that creates a spiralling leading edge vortex.
Some very small insects use the fling and clap or Weis-
Fogh mechanism in which the wings clap together above the
insect's body and then fling apart. As they fling open, the air gets
sucked in and creates a vortex over each wing. This bound vortex
then moves across the wing and, in the clap, acts as the starting vortex for the other wing. Circulation and
lift are increased,at the price of wear and tear on the wings

9. Many insects can hover by beating their wings rapidly, requiring sideways stabilization as well as lift.
A few insects use gliding flight, without the use of thrust. It is found in some species of arboreal ants,
known as gliding ants.
Evolution
Sometime in the Carboniferous Period, some 350 million years ago, when there were only two major land
masses,insects began flying. How and why insect wings developed, however, is not well understood,
largely due to the scarcity of appropriate fossils from the period of their development in the Lower
Carboniferous. Three main theories on the origins of insect flight are that wings developed from paranotal
lobes, extensions of the thoracic terga; that they are modifications of movable abdominal gills as found on
aquaticnaiads of mayflies; or that they developed from thoracic protrusions used as radiators.
Fossils
Fossils from the Devonian (400 million years ago) are all wingless, but by the Carboniferous (320 million
years ago), more than 10 different genera of insects had fully functional wings. There is little preservation
of transitional forms between the two periods. The earliest winged insects are from this time period
(Pterygota),including the Blattoptera, Caloneurodea, primitive stem-
groupEphemeropterans, Orthoptera and Palaeodictyopteroidea. Very
early Blattopterans (during the Carboniferous) had a very large
discoid pronotum and coriaceous forewings with a distinct CuP vein
(an unbranched wing vein, lying near the claval fold and reaching the
wing posterior margin). Even though the oldest definitive insect
fossil is the Devonian Rhyniognatha hirsti, estimated at 396–407
million years old, it possessed dicondylic mandibles, a feature
associated with winged insects.
During the Permian, the dragonflies Odonata were the dominant aerial predator and probably dominated
terrestrial insect predation as well. True Odonata appeared in the Permian and all are amphibian. Their
prototypes are the oldest winged fossils, go back to the Devonian, and are different from other wings in
every way.Their prototypes may have had the beginnings of many modern attributes even by
late Carboniferous and it is possible that they even captured small vertebrates,for some species had a
wing span of 71 cm.[19]
The earliest beetle-like species during the Permian had pointed, leather like
forewings with cells and pits.Hemiptera, or true bugs had appeared in the form
of Arctiniscytina and Paraknightia having forewings with unusual venation, possibly diverging
from Blattoptera
A single large wing from a species of Diptera in the Triassic (10 mm instead of usual 2–6 mm) was found
in Australia (Mt. Crosby).This family Tilliardipteridae, despite of the numerous 'tipuloid' features,should
be included in Psychodomorpha sensu Hennig on account of loss of the convex distal 1A reaching wing
margin and formation of the anal loop.
Hypotheses
 Paranotalhypothesis: This hypothesis suggests that the insect's wings developed from paranotal
lobes, a preadaptation found in insect fossils that is believed to have assisted stabilization while
hopping or falling. In favor of this hypothesis is the tendency of most insects, when startled while
climbing on branches, to escape by dropping to the ground. Such lobes would have served
asparachutes and enable the insect to land more softly. The theory suggests that these lobes gradually
grew larger and in a later stage developed a joint with the thorax. Even later would appear the
muscles to move these crude wings. This model implies a progressive increase in the effectiveness of
the wings, starting with parachuting, then gliding and finally active flight. Still, lack of substantial

10. fossil evidence of the development of the wing joints and muscles poses a major difficulty to the
theory, as does the seemingly spontaneous development of articulation and venation, and it has been
largely rejected by experts in the field.
 Epicoxal hypothesis:This theory suggested that a possible origin for insect wings might have been the
movable abdominal gills found in many aquatic insects, such as on naiads of mayflies. According to
this theory these trachealgills, which started their way as exits of the respiratory system and over
time were modified into locomotive purposes, eventually developed into wings. The trachealgills are
equipped with little winglets that perpetually vibrate and have their own tiny straight muscles.
 Endite-exite hypothesis:The hypothesis with perhaps the strongest evidence is that which stems from
the adaptation of endites and exites, appendages on the respective inner and outer aspects of the
primitive arthropod limb. This was advanced by Truemanbased on a study by Goldschmidt in 1945
on Drosophila melanogaster, in which a pod variation displayed a mutation transforming normal
wings to what was interpreted as a triple-jointed leg arrangement with some additional appendages
but lacking the tarsus,where the wing's costal surface normally would be. This mutation was
reinterpreted as strong evidence for a dorsal exite and endite fusion, rather than a leg, with the
appendages fitting in much better with this hypothesis. The innervation, articulation and musculature
required for the evolution of wings are already present in podomeres.
 Paranota plus leg gene recruitment hypothesis:The fossil larvae of Coxoplectoptera provided
important new clues to the disputed question of the evolutionary origin of insect wings. Before the
larvae fossil discovery the paranotal-hypothesis and the leg-exite-hypothesis have been considered as
incompatible alternative explanations, which have both been supported by a set of evidences from
the fossil record, comparative morphology, developmental biology and genetics. The expression of
leg genes in the ontogeny of the insect wing has been universally considered as conclusive evidence
in favour of the leg-exite-hypothesis, which proposes that insect wings are derived from mobile leg
appendages (exites). However, the larvae of Coxoplectoptera show that the abdominal gills of
mayflies and their ancestors,which are generally considered as corresponding structures to insect
wings, articulated within the dorsal tergite plates. This cannot be seen in modern mayfly larvae,
because their abdominal tergites and sternites are fused to rings, without any traces left even in
embryonic development. If larval gills and wings are corresponding ("serial homologous") structures
and thus share the same evolutionary origin, the new results from Coxoplectoptera demonstrate that
also wings are of tergal origin, as proposed by the classical paranotal-hypothesis. Staniczek, Bechly
& Godunko (2011) therefore suggested a new hypothesis that could reconcile the apparently
conflicting evidence from paleontology and developmental genetics: wings first originated as stiff
outgrowths of tergal plates (paranota),and only later in evolution became mobile, articulated
appendages through secondary recruiting of leg genes.
Suggestions have been made that wings may have evolved initially for sailing on the surface of water as
seen in some stoneflies. An alternative idea is that it drives from directed aerial gliding descent—a
preflight phenomena found in some apterygote, a wingless sister taxa to the winged insects. The earliest
Diagram of different theories
A Hypothetical wingless ancestor
B Paranotal theory:
Hypothetical insect with wings from the
back (Notum)
C Hypothetical insect with wings from
page (Pleurum)
D Epicoxal theory
Hypothetical insect with wings from
Annex of the legs
1 Notum (back)
2 Pleurum (page)
3 Exit (outer attachments of the legs)

11. fliers were similar to dragonflies with two sets of wings, direct flight muscles, and no ability to fold their
wings over their abdomens. Most insects today, which evolved from those first fliers, have simplified to
either one pair of wings or two pairs functioning as a single pair and using a system of indirect flight
muscles.
Natural selection has played an enormous role in refining the wings, control and sensory systems, and
anything else that affects aerodynamics or kinematics. One noteworthy trait is wing twist. Most insect
wings are twisted, as are helicopter blades, with a higher angle of attack at the base. The twist generally is
between 10 and 20 degrees. In addition to this twist, the wing surfaces are not necessarily flat or
featureless; most larger insects have wing membranes distorted and angled between the veins in such a
way that the cross-section of the wings approximates an airfoil. Thus, the wing's basic shape already is
capable of generating a small amount of lift at zero angle of attack (see Insect wing). Most insects control
their wings by adjusting tilt, stiffness, and flapping frequency of the wings with tiny muscles in
the thorax (below). Some insects evolved other wing features that are not advantageous for flight, but play
a role in something else, such as mating or protection.
Some insects, occupying the biological niches that they do, need to be incredibly maneuverable. They
must find their food in tight spaces and be capable of escaping largerpredators – or they may themselves
be predators,and need to capture prey. Their maneuverability, from an aerodynamic viewpoint, is
provided by high lift and thrust forces. Typical insect fliers can attain lift forces up to three times their
weight and horizontal thrust forces up to five times their weight. There are two substantially different
insect flight mechanisms, and each has its own advantages and disadvantages – just becauseodonates have
a more primitive flight mechanism does not mean they are less able fliers; they are,in certain ways,more
agile than anything that has evolved afterward.
Evolution of the ways the wings at rest to the body to create
wings do not fold
back
(recent
Archaeoptera)
spread laterally (large bubbles)
over the back against one another
(damselflies, mayflies)
Folding
(Neoptera)
wings not foldable (e.g.,stoneflies)
Folding
fan-fold (e.g.,front wings of wasps)
Cross fold (such as the rear wing of the beetle)
Subjects folding (such as the rear wing of the earwigs)

12. Morphogenesis
While the development of wings in insects is clearly defined in those who are members of Endopterygota,
which undergo complete metamorphosis; in these species, the wing develops while in the pupal stage of
the insects life cycle. However,insects that undergo incomplete metamorphosis do not have a pupal stage,
therefore they must have a different wing morphogenesis. Insects such as those that are hemimetabolic
have wings that start out as buds, which are found underneath the exoskeleton, and do not become
exposed until the last instar of the nymph.
The first indication of the wing buds is of a thickening of the hypodermis, which can be observed in insect
species as early the embryo, and in the earliest stages of the life cycle. During the development of
morphological features while in the embryo, or embryogenesis, a cluster of cells grow underneath the
ectoderm which later in development, after the lateral ectoderm has grown dorsally to form wind imaginal
disc. An example of wing bud development in the larvae, can be seen in those of White butterflies
(Pieris). In the second instar the histoblast become more prominent, which now form a pocket-like
structure. As of the third and fourth instars, the histoblast become more elongated. This greatly extended
and evaginated, or protruding, part is what becomes the wing. By the close of the last instar, or fifth, the
wing is pushed out of the wing-pocket, although continues to lie under the old larval cuticle while in its
prepupal stage. It is not until the butterfly is in its pupal stage that the wing-bud becomes exposed, and
shortly after eclosion, the wing begins to expand and form its definitive shape.
The development of tracheation of the wings begin before the wing histoblast form, as it is important to
note that they develop near a large trachea. During the fourth instar, cells from the epithelium of this
trachea become greatly enlarged extend into the cavity of the wing bud, with each cell having developed a
closely coiled tracheole. Each trachcole is of unicellular origin, and is at first intracellular in position;
while tracheae are of multicellular origin and the lumen of each is intercellular in position. The
development of tracheoles, each coiled within a single cell of the epithelium of a trachea,and the
subsequent opening of communication between the tracheoles and the lumen of the trachea,and the
uncoiling and stretching out of the tracheoles, so that they reach all parts of the wing.
In the earlier stages of its development, the wing-bud is not provided with special organs of respiration
such as tracheation, as it resembles in this respect the other portions of the hypodermis of which it is still
a part. It should be noted, however, that the histoblast is developed near a large trachea,a cross-section of
which is shown in, which represents sections of these parts of the first, second, third and fourth instars
respectively. At the same time the tracheoles uncoil, and extend in bundles in the forming vein-cavities of
the wing-bud. At the molt that marks the beginning of the pupal stadium stage,they become functional.
At the same time, the larval tracheoles degenerate; their function having been replaced by the wing
tracheae.
Nomenclature
Most of the nomenclature of insect orders is based on the Ancient Greek word for wing, πτερόν (pteron),
as the suffix –ptera
cientific Name linguistic root
Translation of the
Scientific name
English Name
Anisoptera ἀνισο- (aniso-) Unequal wings Dragonfly
Aptera ἀ- (a-), not Wingless Apterygotans, now obsolete

13. Apterygota
πτερύγιον
(pterygion small wing)
ἀ- (a-), not
Wingless Apterygotans
Coleoptera Κολεός (koleos, sheath) Hardened wings Beetles
Dermaptera
Δέρμα (derma, skin,
leather)
Leather wings Earwigs
Diaphanopterodea
Διαφανής (diaphanes,
transparent or
translucent)
With transparent
wings
diaphanopteroideans
Dictyoptera
Δίκτυον (diktyon,
network)
Wings with netted
venation
Cockroaches,mantises and termites
Diptera Δύο- (dyo-, two) Two wings Flies
Embioptera
ἐ- (en, inside; βίος bios,
life)
Interior living
winged insects
Webspinners
Endopterygota
ἐντός (entos, inside;
πτερύγιον, small wing)
Inside wings Holometabolous insects
Ephemeroptera
ἐφήμερος
(ephemeros about one
day long)
Short lived winged
insects
Mayflies
Exopterygota ἔξω (exo, external)
Outdoor flying
insects
Insects that undergo incomplete
metamorphosis
Hemiptera ἡμι- (hemi-, half) Halfwinged insects
Hemiptera (true bugs, leafhoppers,
aphids, etc.)
Heteroptera
ἑτερο- (hetero-,
different)
Different winged True bugs
Homoptera ὅμο- (homo-, similar) Same winged now obsolete
Hymenoptera
ὑμένιον (hymenion,
membrane)
Insects with wings
of thin membranes
bees,wasps, ants, etc.
Isoptera ἶσον (ison, equal) Same winged Termites

14. Lepidoptera Λεπίς (lepis, scale) Scaled wings Butterflies & Moths
Lonchopteridae Λόγχη (lonchi, lance) Lance wings Lance flies
Mecoptera μῆκος (mekos, length) Long wings Snake flies, etc.
Megaloptera
Μεγαλο- (megalo-,
large)
Large wings Dobsonflies, fishflies
Neuroptera νεῦρον (neuron, vein) Veined wing Lacewings, owlflies, antlions, etc.
Neoptera νέος (neos, new, young) New wings
Includes all currently living orders
of flying insects except mayflies
and dragonflies
Oligoneoptera
ὀλίγον- (oligon-, few)
νέος (neos or new)
New with little veins Division of the Neoptera
Orthoptera ὀρθο (ortho-, straight) Straight wings
Grasshoppers, katydids, and
crickets
Palaeodictyoptera
Παλαιός (palaios-, old)
δίκτυον
(diktyon meaning
network)
Old veined wings
Primitive palaeozoic paleopterous
insects
Palaeoptera Παλαιός (Palaios, old) Old wings
Mayflies, dragonflies, and several
fossil orders
Paraneoptera
Παρα- (Para-) νέος
(neos, new)
Part of Neoptera,
mostly with piercing
mouthparts
True bugs, lice, barklice, thrips
Phthiraptera
Φθείρ (phtheir, lice)
ἀ, a-, not
Lice without wings Animal lice
Plecoptera Πλέκειν (plekein, fold) Folded wings Stoneflies
Polyneoptera
Πολύς (polys, many
νέοςneosnew)
Many veined wings
Neoptera with hemimetabolous
development
Psocoptera Ψώχω (psocho, to rub) Rubbing wings Barklice, booklice
Pterygota
Πτερύγιον (pterygion,
Winged insects In class, unlike Apterygota,
including winged and wingless

15. wing) secondary systems
Raphidioptera ῥαφίς (rhaphis, needle) Needle wings Snakeflies
Siphonaptera
Σίφων (siphon, tube)
ἀ- or without
Wingless siphon Fleas
Strepsiptera
Στρέψις (strepsis, to turn
around)
Rotating or twisted
wings
twisted-winged parasites
Thysanoptera
Θύσανοι (thysanoi,
fringes)
Fringe winged Thrips
Trichoptera Τρίχωμα (trichoma, hair) Haired wings Caddisflies
Zoraptera
Ζωρός (zōros meaning
strong)
Strong wings Zorapterans
Zygoptera
ζεῦγος (zeugos meaning
pair)
Paired wings Damselflies
Adaptations
Variation
Insect wings are fundamental in identifying and classifying species as there is no other set of structures in
studying insects more significant. Each order and insect family has distinctive wing shapes and features.
In many cases,even species may be distinguished from each other by differences of color and pattern. For
example, just by position one can identify species, albeit to a much lesser extent. Though most insects
fold their wings when at rest, dragonflies and some damselflies rest with their wings spread out
horizontally, while groups such as the caddisflies, stoneflies, alderflies, and lacewings hold their wings
sloped roof-like over their backs. A few moths wrap their wings around their bodies, while many flies and
most butterflies close their wings together straight upward over the back.

16. Many times the shape of the wings correlates with the type of insect flight. The best-flying insects tend to
have long, slender wings. In many species of Sphingidae (sphinx moths), the forewings are large and
sharply pointed, forming with the small hind wings a triangle that is suggestive of the wings of fast,
modern airplanes. Another, possibly more important correlation, is that of the size and power of the
muscles to the speed and power of flight. In the powerfully flying insects, the wings are most adapted for
the stresses and aerodynamics of flight. The veins are thicker, stronger, and closer together toward the
front edge (or "leading edge") and thinner yet flexible toward the rear edge (or "trailing edge"). This
makes the insect wing an excellently constructed airfoil, capable of exerting both propulsion and lift while
minimizing drag.
Variation of the wing beat may also occur, not just amongst different species,but even among individuals
at different times. In general, the frequency is dependent upon the ratio between the power of the wing
muscles and the resistance of the load. Large-winged, light-bodied butterflies may have a wing beat
frequency of 4–20 per second whereas small-winged, heavy-bodied flies and bees beat their wings more
than 100 times a second and mosquitoes can beat up to 988–1046 times a second. The same goes for
flight; though it is generally difficult to estimate the speed of insects in flight, most insects can probably
fly faster in nature than they do in controlled experiments.
Coleoptera
In species of Coleoptera (beetles), the only functional wings are the hind wings. The hind wings are
longer than the elytra, folded longitudinally and transversely under the elytra. The wing is rotated
forwards on its base into flight position.
Cross folding in the wings of beetles
The hind wing, spread: by folding lines, it is divided into five
fields that are completed each to the rear.
The same wing, half folded: The two joints of the cross-folding
form an obtuse angle. The right is already in the wings folded in
three layers. With greater resolution, the third arch of the wing
margin in the first and second is visible. To the left of the fifth
arch appears in the fourth.

17. The same wing, folded completely: The five fields are aligned
(The elytra have been removed).
This action spread the wing and unfolded longitudinally and transversely. There is the spring mechanism
in the wing structure,sometimes with the help of abdomen movement, to keep the wing in folded
position. The beetle wing venation is reduced and modified due to the folding structure,which include:
 Costa (C), Subcosta posterior (ScP) – at the leading wing marginal, fused for most of the length.
 Radius anterior (RA) – divided into two branches beyond the middle of the wing.
 Radius posterior (RP) – basalconnection is lost.
 Media posterior (MP) – branches,long and strong vein.
 Cubitus anterior (CuA)
 Anal veins (AA,AP) – veins behind the cubitus, separated by anal fold.
In most species of beetles, the front pair of wings are modified and sclerotised (hardened) to
form elytra and they protect the delicate hindwings which are folded beneath.The elytra are connected to
the pterathorax; being called as such because it is where the wings are connected (pteron meaning "wing"
in Greek). The elytra are not used for flight, but tend to cover the hind part of the body and protect the
second pair of wings (alae). The elytra must be raised in order to move the hind flight wings. A beetle's
flight wings are crossed with veins and are folded after landing, often along these veins, and are stored
below the elytra. In some beetles, the ability to fly has been lost. These include someground
beetles (family Carabidae) and some "true weevils" (family Curculionidae), but also some desert and
cave-dwelling species of other families. Many of these species have the two elytra fused together,
forming a solid shield over the abdomen. In a few families, both the ability to fly and the elytra have been
lost, with the best known example being theglow-worms of the family Phengodidae, in which the females
are larviform throughout their lives.
Lepidoptera
The two pairs of wings are found on the middle and third segment,
or mesothorax and metathorax respectively. In the more recent genera,the wings of the second segment
are much more pronounced, however some more primitive forms have similarly sized wings of both
segments. The wings are covered in scales arranged like shingles, forming the extraordinary variety seen
in color. The mesothorax is evolved to have more powerful muscles to propel moth or butterfly through
the air, with the wing of said segment having a stronger vein structure. The largest
superfamily, Noctuidae, has the wings modified to act as Tympanal or hearing organs.
Modifications in
the wing's venation include:
 Costa (C) – not found in Butterflies.
 Subcosta (Sc) + Radius 1 (Sc+R1) – at the leading wing marginal, fused or very close for most of the
length, in hind wing fused and well developed in the humeral area,subcosta never branches in
butterfly.
 Radius (R2-R5) – radius divides into branches beyond the middle of the wing up to five branches in
Papilionidae. On forewing, the last R is stalked in all butterflies except Hesperiidae is separated.
 Radius sector (Rs) – in hind wing.
 Media (M1-M3) – the basal section has been lost.

18.  Cubitus anterior (CuA1-CuA2) – CuP section has been lost.
 Anal veins (A, 1A+2A, 3A) – either one vein A, or two veins 1A+2A, 3A.
 Humeral vein – The hind wing of most butterflies has the humeral vein, except Lycaenidae There is
the enlargement of the humeral area of the hind wing which is overlapped with the fore wing. The
humeral vein strengthened the hind wing overlapped area so that the two wings coupling better.
The wings, head parts of thorax and abdomen of Lepidoptera are covered with minute scales,from which
feature the order 'Lepidoptera' derives its names, the word "lepteron" inAncient Greek meaning 'scale'.
Most scales are lamellar, or blade-like and attached with a pedicel, while other forms may be hair-like or
specialized as secondary sexual characteristics. The lumen or surface of the lamella, has a complex
structure. It gives color either due to the pigmentary colors contained within or due to its three-
dimensional structure. Scales provide a number of functions, which include insulation, thermoregulation,
aiding gliding flight, amongst others, the most important of which is the large diversity of vivid or
indistinct patterns they provide which help the organism protect itself by camouflage, mimicry, and to
seek mates.
Odonata
Species of Odonata (Damselflies and dragonflies) both have two pairs of wings which are about equal in
size and shape and are clear in color. There are five, if the R+M is counted as 1, main vein stems on
dragonfly and damselfly wings, and wing veins are fused at their bases and the wings cannot be folded
over the body at rest,which also include
 Costa (C) – at the leading edge of the wing, strong and marginal, extends to the apex of the wing.
 Subcosta (Sc) – second longitudinal vein, it is unbranched, joins C at nodus.
 Radius and Media (R+M) – third and fourth longitudinal vein, the strongest vein on the wing, with
branches,R1-R4, reach the wing margin, the media anterior (MA) are also reach the wing margin.
IR2 and IR3 are intercalary veins behind R2 and R3 respectively.
 Cubitus (Cu) – fifth longitudinal vein, cubitus posterior (CuP) is unbranched and reach the wing
margin.
 Anal veins (A1) – unbranched veins behind the cubitus.
 A nodus is formed where the second main vein meets the leading edge of the wing. The black
pterostigma is
carried near the
wing tip.
The main veins
and the
crossveins form
the wing
venation
pattern. The
venation patterns are different in different species. There may be very numerous crossveins or rather few.
The Australian Flatwing Damselfly's wings are one of the few veins patterns. The venation pattern is
useful for species identification. Almost all Anisoptera settle with the wings held out sideways or slightly
downward, however most Zygoptera settle with the wings held together, dorsal surfaces apposed. The
thorax of Zygoptera is so oblique that when held in this way the wings fit neatly along the top of the
abdomen. They do not appear to be held straight up as in butterflies or mayflies. In a few zygopteran
families the wings are held horizontally at rest,and in one anisopteran genus
(e.g. Cordulephya, Corduliidae) the wings are held in the typical damselfly resting position. Adult species
possess two pairs of equal or subequal wings. There appear to be only five main vein stems. A nodus is
formed where the second main vein (subcosta) meets the leading edge of the wing. In most families a

19. conspicuous pterostigma is carried near the wing tip. Identification as Odonata can be based on the
venation. The only likely confusion is with some lacewings (order Neuroptera) which have many
crossveins in the wings. Until the early years of the 20th century Odonata were often regarded as being
related to lacewings and were given the ordinal name Paraneuroptera,but any resemblance between these
two orders is entirely superficial. In Anisoptera the hindwing is broader than the forewing and in both
wings a crossvein divides the discoidal cell into a Triangle and Supertriangle
Orthoptera
Species of Orthoptera (Grasshoppers and crickets) have forewings that are tough opaque tegmina, narrow
which are normally covering the hind wings and abdomen at rest. The hind wings are board membranous
and folded in fan-like manner, which include the following venation:
 Costa (C) – at the leading marginal of the forewing and hind wing, unbranched.
 Subcosta (Sc) – second longitudinal vein, unbranched.
 Radius (R) – third longitudinal vein, branched to Rs in forewing and hind wing.
 Media anterior (MA) – fourth longitudinal vein, branched in basal part as Media posterior (MP).
 Cubitus (Cu) – fifth longitudinal vein, on forewing and hind wing dividing near the wing base into
branched CuA, and unbranched CuP.
 Anal veins (A) – veins behind the cubitus, unbranched, two in forewing, many in hind wing.
Phasmatodea
 Costa (C) – at the leading marginal of the hind wing, unbranched, absent in forewing.
 Subcosta (Sc) – second longitudinal vein, unbranched.
 Radius (R) – third longitudinal vein, branched to Rs in
hind wing, unbranched in forewing.
 Media anterior (MA) – fourth longitudinal vein,
branched in basalpart as Media posterior (MP).
 Cubitus (Cu) – fifth longitudinal vein, unbranched.
 Anal veins (A) – veins behind the cubitus, unbranched,
two in forewing, many in hind wing 1A-7A in one
group and the rest in another group.
Stick insect have forewings that are tough, opaque tegmina,
short and covering only the base part of the hind wings at rest. Hind wings from costa to Cubitus are
tough and opaque like the forewings. The large anal area are membranous and folded in fan-like manner.
There are no or very few branching in Stick Insect wing veins.
Dermaptera
Other orders such as the Dermaptera (earwigs), Orthoptera (grasshoppers, crickets), Mantodea (praying
mantis) and Blattodea (cockroaches) have rigid leathery forewings that aren't used for flying, sometimes
called tegmen (pl. tegmina), elytra, or pseudoelytron.
Hemiptera
In Hemiptera (true bugs), the forewings may be
hardened, though to a lesser extent than in the beetles.
For example, the anterior part of the front wings of stink
bugs is hardened, while the posterior part is
membranous. They are
called hemelytron (pl. hemelytra). They are only found
in the suborder Heteroptera; the wings of

20. the Homoptera, such as thecicada,are typically entirely membranous. Both forewings and hindwings of
Cicada are membranous, most species are glass-like although some are opaque. Cicadas are not good
fliers and most fly only a few seconds. When flying, forewing and hind wing are hooked together by a
grooved coupling along the hind wing costa and forewing margin. Most species have a basic venation as
shown in the following picture.
 Costa (C) – at the leading wing marginal, in forewing extends to the node and lies close to Sc+R.
 Subcosta + Radius (Sc+R) – in forewing Sc and R fused together to the node. Radial sector (Rs)
arises near the node and unbranches.
 Radius anterior (RA)
 Radius posterior (RP)
 Media (M) – branches to M1 to M4.
 Cubitus anterior (CuA) – branches to CuA1 and CuA2.
 Cubitus posterior (CuP) – unbranches.
 Anal veins (A) – veins behind the cubitus, 1A and 2A fused in the forewing, CuP and 2A are folded.
Also notice there are the ambient veins and peripheral membranes on the margin of both wings.
In the Diptera (true flies), there is only one pair of functional wings, with the posterior pair of wings are
reduced to halteres, which help the fly to sense its orientation and movement, as well as to improve
balance by acting similar to gyroscopes. In Calyptratae, the very hindmost portion of the wings are
modified into somewhat thickened flaps calledcalypters which cover the halteres.
 Costa (C) – not found in Diptera.
 Subcosta (Sc) – became the leading wing vein, unbranched.
 Radius (R) – branched to R1-R5.
 Media (M) – branched to M1-M4.
 Cubitus anterior(CuA)- unbranched, CuP is reduced in Diptera. Some species CuA and 1A are
separated,some species meets when reaching the wing margin, some species fused.
 Anal veins (A) – only two anal veins 1A and 2A are present,2A is not distinctive in some species.
 Discal Cell (dc) – well defined in most species.
Blattodea
Species of Blattodea (cockroaches) have a forewing, are also known as tegmen, that is more or less
sclerotized. It is used in flight as well as a form of
protection of the membranous hind wings. The
veins of hind wing are about the same as front wing
but with large anal lobe folded at rest between CuP
and 1A. The anal lobe usually folded in a fan-like
manner.
 Costa (C) – at the leading edge of the wing.
 Subcosta (Sc) – second longitudinal vein, it is relatively short.
 Radius (R) – third longitudinal vein, with many pectinate branches.
 Media (M) – fourth longitudinal vein, reach the wing margin.

21.  Cubitus anterior (CuA) – fifth longitudinal vein, with dichotomous branches occupy large part of
tegmen.
 Cubitus posterior (CuP) – is unbranched, curved and reach the wing margin.
 Anal veins (A) – veins behind the cubitus.
Hymenoptera
The Hymenoptera adults, include sawflies, wasps,bees and non-working ants, all of which have two pairs
of membranous wings.
 Costa (C) – not found in Hymenoptera.
 Subcosta (Sc) – unbranched.
 Radius (R) – branched to R1-R5.
 Media (M) – M is unbranched, in forewing M is fused with Rs for part of its length.
 Cubitus (CuA) – unbranched, CuP is absent in Hymenoptera.
 Anal veins (A) – only two anal veins 1A and 2A are present,2A is not distinctive in some species.
 Wing-coupling – Row of hooks on the leading edge of hind wing engage the hind margin of the
forewing, strongly couple the wings in flight.
 Line of wing folding – Some species,including Vespidae, the forewing are longitudinally folded
along the 'line of wing folding' at rest.
 Pterostigma – is present for some species.
The forward margin of the hind wing bears a number of hooked bristles, or "hamuli", which lock onto the
fore wing, keeping them held together. The smaller species may have only two or three hamuli on each
side, but the largest wasps may have a considerable number, keeping the wings gripped together
especially tightly. Hymenopteran wings have relatively few veins compared with many other insects,
especially in the smaller species.
Other families
Termites are relatively poor fliers and are readily blown downwind in wind speeds of less than 2 km/h,
shedding their wings soon after landing at an acceptable site, where they mate and attempt to form a nest
in damp timber or earth. Wings of most termites have three heavy veins along the basal part of the front
edge of the forewing and the crossveins near the wing tip are angled, making trapezoidal cells. Although
subterranean termite wings have just two major veins along the front edge of the forewing and the cross
veins towards the wingtip are perpendicular to these veins, making square and rectangular cells.
Species of Thysanoptera (thrips) have slender front and hind wings with long fringes of hair, called
fringed wings. While species of Trichoptera (caddisfly) have hairy wings with the front and hind wings
clothed with setae
References
 Triplehorn, Charles A.; Johnson Norman F. (2005). Borror and DeLong's introduction to the study of
insects (7th ed.). Thomson Brooks/Cole. ISBN 0-03-096835-6.